Rheological additives are chemical compositions, which, added even in small amounts, modify a liquid system's rheological properties, such as viscosity and response to shear. Such additives or thickeners may be used in a variety of liquid systems including aqueous systems such as paints, aqueous inks, and personal care products and compositions for treating subterranean formations. The additives improve the rheological properties by also affecting the dispersion, suspension and emulsification of pigments, binders and other solids within a vehicle.
Thixotropic promoters are a category of rheology additives widely used in the coating industry. They can be categorized as organic clay, polyethylene waxes and titanium derivatives. These thixotropic promoters have been used for a long time in latex paints and other architectural coatings. Many types of thixotropic promoters are used because each of them has its own limitations. Some, such as the organic clay, are very effective but they have disadvantages such as decreasing the gloss of the paint significantly. Thixotropic promoters are also used in hydraulic fracturing of subterranean formations, such as oil and natural gas wells, and other methods of secondary oil recovery.
Hydrophobically modified alkali swellable emulsion (HASE, also known as Hydrophobically modified alkali soluble) polymer systems and alkali soluble emulsion (ASE) polymer systems are commonly employed to modify the rheological properties of aqueous emulsion systems. These polymers are substantially insoluble in water at a low pH. However, at higher pH they become swellable or soluble in water and thus exhibit thickening behavior. Under the influence of a base, organic or inorganic, the HASE particles gradually swell and expand to form a three-dimensional network by intermolecular hydrophobic aggregation between HASE copolymer chains and/or with components of the emulsion. This network, combined with the hydrodynamic exclusion volume created by the expanded HASE chains, produces a thickening effect. This network is sensitive to applied stress so it breaks down under shear and recovers when the stress is relieved. Such rheological properties are particularly desirable for paints and coatings because they make the formulation easy to apply onto a surface while providing the thickness needed for uniform coverage and avoid spattering.
These alkali-swellable and alkali-soluble polymers are carboxyl functional polymers synthesized by free radical polymerization. HASE copolymer systems can be prepared from the following monomers: (a) an ethylenically unsaturated carboxylic acid, (b) a nonionic ethylenically unsaturated monomer, and (c) an ethylenically unsaturated hydrophobic monomer. Representative HASE copolymer systems include those shown in EP 226097 B1, EP 705852 B1, U.S. Pat. No. 4,384,096, U.S. Pat. No. 5,874,495, U.S. Pat. No. 7,217,752 B2, and US patent application publication 2006/0270563 A1, now U.S. Pat. Nos. 7,772,421 and 8,071,674, all incorporated herein by reference.
Three categories of polymers produced by emulsion polymerization are: (1) Synthetic rubber: some grades of styrene-butadiene (SBR), some grades of polybutadiene, polychloroprene (Neoprene), nitrile rubber, acrylic rubber, fluoroelastomer (FKM); (2) Plastic: some grades of PVC, some grades of polystyrene, some grades of PMMA (polymethylmethacrylate), acrylonitrile-butadiene-styrene terpolymer (ABS), polyvinylidene fluoride, polytertrafluoroethylene (PTFE); and (3) Dispersions (i.e., polymers sold as aqueous dispersions).
Latex is an example of an emulsion polymer which is a water based polymer dispersion. Latex paints are used for a variety of applications including interior and exterior, and flat, semi-gloss and gloss applications. Latex is a stable dispersion (colloidal emulsion) of rubber or plastic polymer microparticles in an aqueous medium. Latexes may be natural or synthetic.
It would be desirable to have a as a thixotropic promoter that provides improved viscosity control, sagging, and leveling, while maintaining gloss in latex paints and coatings.
Hydraulic fracturing of the subterranean formation is conducted to increase oil and/or gas production. Fracturing is caused by injecting a viscous fracturing fluid or a foam at a high pressure (hereinafter injection pressure) into the well to form a fracture. As the fracture is formed, the particulate material, referred to as a “propping agent” or “proppant” is placed in the formation to maintain the fracture in a propped condition when the injection pressure is released. Coated and/or uncoated particles are often used as proppants to keep open fractures imposed by hydraulic fracturing upon a subterranean formation, e.g., an oil or gas bearing strata. Particles typically used to prop fractures generally comprise sand or sintered ceramic particles as the fracture forms, the proppants are carried into the fracture by suspending them in additional fluid or foam to fill the fracture with slurry of proppant in the fluid or foam. Upon release of the pressure, the proppants form a pack that serves to hold open the fractures. Thus, the proppants increase production of oil and/or gas by providing a conductive channel in the formation. There is a need for a proppant carrier that can prevent settling of proppants or sand being positioned in the fractures.
During primary recovery a subterranean formation produces the oil by pressure depletion. In pressure depletion, the pressure difference between the formation and a production well or wells forces the oil contained within the formation toward a production well where it can be recovered. Typically, up to 35 percent of the oil initially contained in a formation can be recovered using pressure depletion. Methods have been developed to recover oil which could not be recovered using only pressure depletion techniques or secondary recovery techniques. These methods are typically referred to as “enhanced oil recovery techniques” (EOR).
One enhanced oil recovery process is referred to as surfactant flooding. This generally covers the use of an aqueous fluid containing surfactant injected into an oil rich formation to displace oil from the formation and the displaced oil is then recovered.
Another enhanced oil recovery process is referred to as chemical flooding. This generally covers the use of polymer and/or surfactant slugs. In polymer flooding, a polymer solution is injected to displace oil toward producing wells. The polymer solution is designed to develop a favorable mobility ratio between the injected polymer solution and the oil/water bank being displaced ahead of the polymer. In surfactant flooding, an aqueous solution containing surfactant is injected into the oil rich formation. Residual oil drops are deformed as a result of low interfacial tension provided by surfactant solution and drops are displaced through the pore throats and displaced oil is then recovered.
U.S. Pat. No. 4,432,881, incorporated herein by reference in its entirety, discloses an aqueous liquid medium having increased low shear viscosity as provided by dispersing into the aqueous medium (1) a water-soluble polymer having pendant hydrophobic groups, e.g., an acrylamide dodecyl acrylate copolymer, and (2) a water-dispersible surfactant, e.g., sodium oleate, or dodecyl polyethyleneoxy glycol monoether.
U.S. Pat. No. 4,541,935, incorporated herein by reference in its entirety, discloses fracturing processes which use aqueous hydraulic fracturing fluids. The fluids comprise: (a) an aqueous medium, and (b) a thickening amount of a thickener composition comprising (i) a water-soluble or water-dispersible interpolymer having pendant hydrophobic groups chemically bonded thereto, (ii) a nonionic surfactant having a hydrophobic group(s) capable of associating with the hydrophobic groups on said organic polymer, and (iii) a water-soluble electrolyte.
U.S. Pat. No. 5,566,760, incorporated herein by reference in its entirety, discloses a fracturing fluid comprising surfactants and hydrophobically-modified polymers.
U.S. Pat. No. 7,084,095, incorporated herein by reference in its entirety, discloses addition of polymers to a viscoelastic surfactant base system allows adjusting the rheological properties of the base fluid.
U.S. Pat. No. 7,427,583, incorporated herein by reference in its entirety, describes an aqueous viscoelastic fracturing fluid for use in the recovery of hydrocarbons. The fluid comprises a viscoelastic surfactant and a hydrophobically modified polymer.
U.S. Pat. No. 7,727,937 to Pauls et al, incorporated herein by reference in its entirety, discloses acidic treatment fluids used in industrial and/or subterranean operations, and more particularly, acidic treatment fluids comprising clarified xanthan gelling agents, and methods of use in industrial and/or subterranean operations.
U.S. Pat. No. 7,772,421 to Yang et al, incorporated herein by reference in its entirety, discloses a hydraulic fracturing composition comprising water, a pH responsive polymer and a proppant.
U.S. Pat. No. 7,789,160 to Hough et al, incorporated herein by reference in its entirety discloses an aqueous fluid useful for the recovery of crude oil from a subterranean formation, which includes a composition including a mixture of water, a water soluble block copolymer, an inorganic salt and at least one member of the group of a nonionic surfactant having an HLB of less than 12, and methods for using same.
U.S. Pat. No. 7,857,055 to Li et al, incorporated herein by reference in its entirety, discloses a fluid for treating a subterranean formation comprising an aqueous solution of a polysaccharide, a polyacrylamide, a crosslinking agent, and less than 0.1% by weight of any clay component, wherein the polyacrylamide is present in an amount of from about 0.01 percent to about 1 percent by weight of the fluid.
It would be desirable to provide stable fracturing fluids and EOR fluids for subterranean formations, such as natural gas and/or oil field.
Also, there is a need to enhance viscosity to improve personal care compositions. In personal care applications, consumers are increasingly demanding formulations that provide multiple benefits such as, but not limited to, unique sensory experience, enhanced moisturization, increased conditioning, improved delivery of active ingredients and compatibility. Synthetic rheology modifier polymers can be employed to assist in achieving one or more of these properties.
Also there is a need to enhance viscosity to improve cleaning compositions for home and industry.